Application of high loss dielectrics to wave guide transmission systems



3U, w50 G. L. FERNSLER 2,510,016

APPLICATION oF HIGH Loss nIELEcIRIcs Io WAVE GUIDE TRANSMISSION SYSTEMS original Filed April 29, 194:5

. 'Illini' Cttormcgv Il N 4 Patented May 30, 1950 APPLICATION OF HIGH LOSS DIELECTRICS TO TEMS WAVE GUIDE TRANSMISSION SYS- George L. Fernsler, Lawrenceville, N. J., assignor to Radio Corporation of America, a corporation of Delaware Original application April 29, 1943, Serial No.

485,012. Divided and this application December 11, 1946, Serial No. 715,426

4 Claims.

This application is a division of my copending U. S. application Serial No. 485,012, led April 29, 1943, now Patent No. 2,465,719, granted March 29, 1949, and assigned to the same assignee as the instant application.

This invention relates generally to super-high frequency apparatus and more particularly to an improved method of and means for preventing leakage of super-high frequency energy between relatively movable conductive elements of a wave guide transmission system.

The instant invention includes improvements upon the apparatus disclosed in the copending U. S. application of Ernest G, Linder, Serial No. 485,357, filed May 1, 1943, now Patent No. 2,443,- 109, granted June 8, 1948, in which is described the use of conductive rubber having relatively low resistivity for attenuating super-high frequency energy.

Among the objects of the invention are to provide an improved method of and means for attenuating super-high frequency energy in a wave guide transmission system. Another object of the invention is to provide an improved method of and means for preventing leakage of superhigh frequency energy between relatively movable conductive elements of a wave guide system. A further object of the invention is to provide an improved method of and means for preventing leakage of super-high frequency energy along an adjusting device for a matching stub incorporated in a wave guide transmission system.

An additional object of the invention is to` provide an improved method of and means for minimizing leakage of super-high frequency energy along external adjusting means for a snorting plug within a super-high frequency Wave guide transmission system. Another object is to provide an improved structure for moving relatively two matching stubs along the axis of wave propagation in a super-high frequency Wave guide transmission system wherein leakage of super-high frequency energy is minimized by energy-absorptive material secured to the wave guide adjacent the relatively movable conductive elements thereof.

The invention will be described in further detail by reference to the accompanying drawing of which Figure 1 is a cross-sectional perspective view of one embodiment thereof, and Figures 2, 3, and 4 are cross-sectional views of modications of a second embodiment thereof. Similar reference numerals are applied to similar elements throughout the drawing.

Figure 1 shows a Wave guide I which includes a longitudinal slot 2 extending along a predetermined length of one face of the wave guide I. A U-shaped bracket 3 of conductive material is shaped to conform to the outside dimensions of the wave guide I and arranged to slide longitudinally thereof. The bracket 3 includes slotted holes S, which may be employed for clamping the bracket at any predetermined position longitudinally of the wave guide I. The bracket 3 is apertured to receive a concentric transmission line 4 which may be disposed at any desired angle with respect thereto. The outer conductor of the transmission line 4 should be soldered, or otherwise electrically connected, to the bracket 3 while the inner conductor of the concentric line extends through the aperture in the bracket 3 and also through the slot 2 of the wave guide I. It will be seen that the inner conductor of the concentric transmission line 4 will therefore provide a wave probe for pickup of super-high frequency energy within the wave guide and that this probe may be moved longitudinally along the wave guide by shifting the U-shaped bracket 3.

A flat layer of super-high frequency energyabsorptive material 5 such as, for example, conductive rubber having relatively low resistivity, is secured to the inside surface of the central portion of the U-shaped bracket 3 by means of oval-headed rivets 6. The rivets 6 should preferably be irregularly spaced, and well separated from the concentric line 4. The conductive rubber layer 5 will therefore occupy most of the space between the lcentral portion of the U-shaped bracket 3 and the slotted face of the wave guide I. The rubber layer should be apertured to accommodate the inner conductor of the concentric transmission line 4. The rubber layer 5 will attenuate substantially all leakage energy between the wave guide and the U-shaped bracket 3 while the rivets 6 will provide electrical contact between the bracket and wave guide. Since the conductive rubber layer has relatively low resistivity, the effects of erratic contact between the movable metal parts will be minimized and will provide less interference in the concentric line output circuit, since the field near the rivets which slide on the wave guide I is relatively weak due to the high conductive currents through the rubber layer. A conductive rubber layer having a resistivity of 5 ohm-centimeters appears to be entirely satisfactory, and to prevent substantially all erratic contact eiects as the probe is moved longitudinally along the wave guide. It will be seen that yjusting shaft I3 within the wave guide I.

.the concentric conductive element I6.

applicants improved structure substantially eliminates two of the most troublesome features of movable elements in super-high frequency wave guide transmission systems, since energy leakages and erratic contact between movable parts normally seriously affect the accuracy of measurements in such systems. The transmission line 4 may be connected to a crystal detector or other utilization apparatus, not shown.

Figure 2 includes a wave guide I, having a snorting plug I 2, which is movable longitudinally along the wave guide I. Adjustment of the snorting plug I2 may be accomplished externally by means of a shaft I3 which extends through a central aperture in a conductive wave guide terminating plate Iii. A knob I5, may be Yfastened to the external end of the adjusting shaft I3.

To prevent leakage of super-high frequency energy past the snorting plug I2, and around the adjusting shaft I3 in the vicinity of the apertured terminating plate I4, a super-high Afrequency attenuator is provided which effectively prevents energy leakage without affecting the -operation of the snorting plug.

,'Ihe attenuator includes a cylindrical conductive member Iii which is concentric with the ad- One end of the cylindrical conductive member I 5 terminated in the wave guide terminating plate I4. A.conductive rubber dielectric Il occupies the space between the adjusting shaft I3 and The adjusting shaft I3, concentric conductive element IB, and high-loss dielectric I? therefore comvprise a coaxial transmission line of very high impedance which effectively prevents leakage of energy outside of the wave guide. Moreover, the

l rubber dielectric will provide a satisfactory bearend of the supporting member 23 adjacent the wave guide I. In order to prevent leakage of' super-high frequency energy past the joint between the conductive plug 2.4, the tuning stub 22 and the supporting member 2 3, the remaining .space within the supporting structure 23 is filled vvithconductive rubber 25. Therefore, -tne sup- ,porting structure 23, the tuning stub 22, and the g conductive rubber layer 25 provide an extremely high impedance concentric transmission line which effectively prevents leakage of super-high frequency energy along the threaded tuning stub 22. The length of the portion of the tuning stub 22, which extends into the wave guide I, may be ,i adjusted by turning an adjusting screw head 2 `attached to the exterior end of the tuning stub Figure Llincludes a wave guide I having two angularly-d-isposed stub lmatching sections 32, 33 v vlfiich include snorting plugs 34, 35, respectively. vThe snorting plugs may be of the type described f in Figure 2 `and leakage of super-high frequency energy past the snorting plugs may be prevented in `the manner described therein. Matching of a wave guide to a series of complex load circuits 'may be greatly facilitated by adjusting the relative spacing of the two guide matching stubs. ."Ihis may be accomplished readily vloy providing .a

telescoping portion 36 of one Vof the wave guide faces whereby the stud 33 may be moved longitudinally of the guide I.

In order to prevent leakage of super-high frequency energy between the telescopic conductive face of the wave guide I and the movable guide face 36, the guide I includes a pair of cover brackets 3'I, 38 to the inner surfaces of which are secured layers of conductive rubber 39, Ml, respectively. Since the cover bracket 3l, the conductive rubber layer 39, the movable guide section 36 and the wave guide I are all in contact, leakage of super-high frequency energy through the telescopic joint will be attenuated effectively due to the resultant high impedance energy path. The arrangement of the cover bracket 3S, the conductive rubber layer 40, the movable guide section 36 and guide I is similar to that just described. Therefore, the movable guide section and tuning stub wave guide 33 may be moved in either direction longitudinally @ions the Wave gui-.dce l to provide predetermined spacing of the guide tuning stubs 32, 33 Without involving appreciable leakage of super-high frequency energy through the sliding joints of the wave guide.

Thus the invention described comprises several embodiments and modifications thereof for preventing leakage of super-high frequency energy between relatively movable yconductive elements in a wave guide transmission system.

I claim as my invention:

l. A super-nigh-frequency wave guide structure having an aperture in one portion thereof to receive at leasta portion of an externally adjustable impedance element including a device for reducing leakage of superhigh frequency energy from between said element and said structure comprising a conductive rubber packing interposed between said adjustable element and said structure, said packing being subjected to sufficient pressure between said movable element and structure to provide substantially uniform con- -tact therewith without deleteriously limiting the movability of said element with respect to said structure.

`2. In a super-nigh frequency wave guide having a slot in one face thereof to receive a super-high frequency probe, a `movable element including an apertured conductive element longitudinally vmovable upon and in electrical contact with ,said guide, a concentric line section supported by said conductive element, the central conductor .of .said line section including a probe extending into said guide through said aperture and said slot, and a conductive rubber element interposed between `said guide and said conductive element and fastened .to said conductive element for reducing leakage o f super-high frequency energy between said guide and said conductive element.

3. `In a super-high frequency wave guidehaving an aperture in one face thereof to receive an vexternally adjustable tuning stub, a device for reducing leakage of super-high frequency energy from said tuning stub comprising a cylindrical i conductive element concentric with a portion of said stub externally of said guide, and .conduce tive rubber forming a partially conductive dielectric extending substantially between said cyl-indrical element and said portion of .said stub. 4. In a super-high frequency wave guide structure including an externally adjustable, axially movable conductive snorting plug, a device for re- .ducing Yleakage of super-nigh frequencygenergy around said snorting plug comprising an apen- 76 -tured conductiveelement closing the end of said 5 guide structure with the externally adjustable portion of said plug extending through said aperture, a cylndraceous conductive element within said guide connected to said apertured element and concentric with said portion of said plug eX- tending to and through said aperture, and a conductive rubber dielectric interposed substantially between said concentric elements to provide thereby a. concentric line attenuator for said leakage energy.

GEORGE L. F'ERNSLERk REFERENCES CITED The following references are of record in the le of this patent:

Number 8 STATES PATENTS Name Date Peters June 29, 1943 Webber July 10, 1945 Okress May 21, 1946 Ring Aug.` 27, 1946 Ginzton Sept. 10, 1946 Moles Oct. 22, 1946 

